Pressure sensitive record material



July 5, 1955 GREEN 2,712,507

PRESSURE SENSITIVE RECORD MATERIAL Filed June 30, 1953 PAPER COATING OFMICROSCOPIC HYDROPHILIC COLLOID RUPTURABLE CAPSULES CONTAINING PRINTINGFLUID INVENTOR BARRETT K. GREEN gwa HIS ATTORNEYS United States Patent 6PRESSURE SENSITIVE RECGRD MATERIAL Barrett K. Green, Dayton, Ohio,assignor to The National Cash Register Company, Dayton, Ohio, acorporation of Maryland Application June 30, 1953, Serial No. 365,184

4 Claims. (Cl. 117-36) This invention relates to manifold recordmaterial, and more particularly pertains to such record material whichhas a transfer coating thereon of microscopic gelled hydrophilic colloidcapsules, each of said capsules consisting of a dense oil-imperviousshell-like wall of filmforming colloid material deposited around anucleus of an oily water-immiscible printing fluid by coacervate forces,said capsules being rupturable by printing or writing pressure appliedto the record material so as to release said printing fluid for transferto an underlying sheet.

The encapsulating material which encloses the oil droplets is a singlegelled hydrophilic colloid material as contrasted with capsules made ofa complex gelled gellable hydrophilic colloid material, whichcharacterizes the encapsulating material of the microscopicoil-containing capsules with which the record material is coated, asdisclosed in application for United States Letters Patent, Serial No.365,198, which was filed on the same day as this application, by thisapplicant and Lowell Schleicher.

The record material of this invention also is .distinguished from thatdisclosed in applicant Greens United States Patent No. 2,374,862, andapplicant Greens and Robert W. Sandbergs United States Patents2,548,366; 2,550,466; 2,550,467; 2,550,468; and 2,550,469, in that inthe patents, instead of using microscopic oil-containing capsules in thetransfer coating, the oily printing fluid was contained in droplet formin a continuous gelled hydrophilic colloid film.

In forming a continuous hydrophilic colloid film, there is a permeablecondition set up whereby, even though the surface of the film ishardened by treatment that closes the surface pores, cracks may formthrough handling, or due to environmental conditions, which rupture thefilm. In such cracks the voids holding the oil are opened up because thecracks run straight through the voids. As the walls separating the voidsin the film are somewhat permeable to the oil, oil may leak out, notonly from the region of the'cracks, but from uncracked portions of thefilm, leaving the film inadequate to perform its function.

In the present invention the microscopic capsules, although adherent toone another and to the paper, maintain their individuality so that ifcracks are made by folding of the paper or otherwise, the cracks in thecoating will run between the capsules and not through them. Also, in thepresent invention the microscopic capsules are made impermeable to theoil by a method disclosed and claimed in applicants co-pendingapplication for United States Letters Patent, Serial No. 365,106, filedthe same day as this application. That method will be described in thisapplication, insofar as applicable, but will not be claimed herein.

The manifold sheet of this invention, therefore, is superior to thoseshown in the patents to which reference has been made, insofar asshelf-life and durability are concerned.

Therefore, it is an object of this invention to provide 2,712,507Patented July 5, 1955 a manifold sheet having a transfer film coating,on a surface thereof, which is composed of microscopic capsules ofgelled hydrophilic colloid material, each of said capsules consisting ofa dense oil-impervious shell-like wall of the colloid material depositedaround a nucleus of an oily printing fluid by coacervate forces, and thecapsules being present in such number as to be in substantialcontiguity.

Inasmuch as the invention contemplates the use of color-reactantmaterials, which constitute the oil, or which form a part of the oil, itis another object of the invention to make such a manifold sheet inwhich the transfer coating is substantially colorless, but which willrender colored marks upon sensitized receiving sheets.

With these and incidental objects in view, the invention includescertain novel features of structure and combinations of elements, apreferred form or embodiment of which is hereinafter described withreference to the drawing which accompanies and forms a part of thisspecification.

The drawing shows the manifold sheet of this invention in an enlargedand exaggerated form, so that the features may be discernible.

In the preferred embodiment of the invention there will be described amanifold sheet containing as the printing mark substance the compound3,3 bis(p-dimethylaminophenyl) 6-dimethylamino phthalide, which iscolorless and forms blue marks when coming into adsorption contact witha record material sensitized with acid claylike material such asattapulgite, or zeolite material, such as sodium aluminum silicatematerial, or such in which the sodium has been exchanged for hydrogen orsome other metal ion, as disclosed in applicants United States LettersPatents No. 2,5 81,186 and No. 2,641,557. As a secondary color-reactantin the oily printing fluid of the preferred embodiment there is provideda type of color reactant which oxidizm from a normally colorless form toa colored form when in contact with the clay materials just described,after the passage of some hours or days. This preferred compound isbenzoyl leuco methylene blue. The phthalide compound, like all triphenylmethane dyes, tends to fade in time, but the secondary color reactant ofthe oxidizing type forms a color which is lasting. The phthalidecompound reacts instantly to form a colored mark, to be supported laterby the color of the oxidized secondary color reactant.

As the oily vehicle in which the color-reactants named above arecarried, applicant has chosen for the preferred embodimenttrichlorodiphenyl, the color reactants being used therein in amountsequal to several percent, by weight, of the total amount of the printingfluid.

As the encapsulating colloid material for the preferred embodiment,applicant has selected a gelatin, although other gellable film-forminghydrophilic colloids, such as agar-agar, will do.

The preferred method of forming the capsules includes the step oftreating an aqueous sol of the colloid material having the oilemulsified therein, with a salt solution to cause the colloid materialto deposit around the oil droplets, and then causing the colloid to gel.In making up the capsular material, one gallon of an oil-in-wateremulsion of 20 parts, by weight, of trichlorodiphenyl containing thecolor reactants, and parts, by weight, of a sol of 10%, by weight, ofpigskin gelatin in water, is prepared, the emulsifying continuing untilthe drop size of the oil is from 2 to 5 microns. This material is keptat 50 centigrade to prevent the gelatin from gelling. With thetemperature of the ingredients still kept at 50 C., coacervation then isinduced by adding, slowly and uniformly, four-tenths of a gallon of 20%,by weight, of sodium sulphate in water. The uniform addition of thismaterial is accomplished by continuous agitation.

, tion of formaldehyde in water.

'To gel the coacervate, the heated coacervate mixture this point theencapsulation of the oil with the gelled hydrophilic colloid materialhas taken place and the further steps are to put it in condition for useas intended. The material is filtered and washed with water, thetemperature being kept below the melting point of the gelatin, to removethe salt. If desired, the filtered material is hardened by combining itwith 2 gallons of a 37% solu- This hardened mass is then filtered andwashed to remove the residual formaldehyde. The resulting filter cake isadjusted to the proper water content by the addition of water or theremoval thereof, by ordinary means such as centrifuging or spray drying,and the material is ready for use. As this material is intended for apaper coating composition, it is kept in aqueous suspension and applieddirectly to the paper, which is then dried, leaving the capsulesadherent to the paper and to each other in a film.

If a portion of this fluid is sparsely dispersed in water and placedunder a microscope, it will be seen to consist of microscopic capsulesof the hydrophilic colloid material, the individual capsules beingseveral microns in diameter and each containing a nucleus of oil. As thewater content is decreased, the capsules tend to form aggregations, likebunches of grapes. When the material is of the right consistency, it iscoated on paper by rollers, spray, brushes, or any other of the commonlyused methods of coating paper, and allowed to dry. The material is ofsuch a nature that the capsules are adherent to each other in thecoating, and will adhere to the paper, without the addition of any otherbinder material.

For more details concerning the process of making the microscopiccapsular material, reference is made to my co-pending application,Serial No. 365,106, regarding the process, to which attention has beendrawn.

Other colorless adsorption color reactants which form color immediatelyon contact with acid clay-like material, such as the mentionedattapulgite, are malachite green lactone, which is 3,3bis(p-dimethylaminophenyl) phthalide, and the ethyl and propylhomologues thereof, which form bluish green marks on the acid-like claysensitized receiving sheet. Other comparable and equivalent materialsare found in United States Patent No. 2,548,366, to which attention hasbeen directed.

The material in the oil which produces the mark on the receiving sheetneed not be a reactive material but may have an intrinsic color ofitself, such as dissolved v dyes, like Sudan III.

The oils which may be substituted for trichloro-diphenyl are any of thewater immiscible oils, which are inert as to the other materials used informing the capsules, such as petroleum fractions like paratfin oil,vegetable oil such as castor oil, and cottonseed oil, animal oils, suchas sperm oil and lard oil, and any other various synthetic oils, such asmethyl salicylate.

The coating material should be used in such quantity on the paper thatwhen dried the coated area will be profusely supplied with themicroscopic capsules, but such thickness need be no more than a fractionof a thousandth of an inch, because the size of the capsules is in termsof several microns. A four pound coating on a ream of paper 25 inches by38 inches is satisfactory.

A sheet of ordinary writing paper, coated on one surface With thedescribed coating composition laid with that coated surface on theattapulgite-sensitized surface of a receiving sheet, forms a manifoldsystem which is responsive to very light printing or writing pressures,such as are ordinarily used in every-day printing and writing, so astomake clear and distinct marks on the receiving sheet, yet the coating isso durable that it will undergo,

rough handling without premature rupture of the capsules and is proofagainst the deleterious influences of the environment, eitheratmospheric 'or artificial.

The capsules may be rendered porous if the gelled material is allowed todry without washing out the salt.

While the form of the invention herein shown and described is admirablyadapted to fulfill the objects primarily stated, it is to be understoodthat it is not intended to confine the invention to the one form orembodiment herein disclosed, for it is susceptible of embodiment invvarious other forms.

What is claimed is:

l. A record material base sheet having on a surface thereof a coatingconsisting of a profusion of microscopic pressurerupturable capsuleshaving walls of gelled film-forming hydrophilic colloid material insubstantial contiguity, each of the capsules consisting of an oilywater-immiscible printing fluid as a central nucleus around which hasbeen evenly deposited by coacervation forces a dense oil-impermeableshell-like coating of the colloid material, said capsules beingrupturable by printing or marking pressures applied to the coated sheet.

2. Paper having coated on a surface thereof microscopic capsules havingwalls of gelledfilm-forming hydrophilic colloid material, the capsulesbeing present in such number that they are in substantial contiguity,and each of said capsules consisting of an oily waterimrniscibleprinting fluid as a central nucleus around which has been evenlydeposited by coacervation forces a dense oil-impermeable coating of thecolloid mate'- rial, said cupsules being rupturable by printing ormarking pressures applied to the coated sheet of paper.

3. A sheet of paper having on a surface thereof a coating that issubstantially colorless, said coating consisting of a profusion ofpressure-rupturable microscopic capsules having walls of gelledfilm-forming hydrophilic colloid material in substantial contiguity,each of the capsules consisting of a dense shell-like oil-impermeableWall of the colloid material deposited about a central nucleus of acolorless oily water-immiscible printing fluid by coacervation forces.

4. The record material of claim 3 in WhlCll'thfi oily printing fluidconsists of a water-immiscible oil vehicle in which is carried acolorless color reactant which turns to a colored form on contact withpaper sensitized by having thereon acid clay-like material.

References Cited in the file of this patent UNITED STATES PATENTS2,183,053 Taylor Dec. 12, 1939 2,410,110 Taylor Oct. 29, 1946 2,548,366Green Apr. 10, 1951 2,550,573 Green Apr. 24, 1951

1. A RECORD MATERIAL BASE SHEET HAVING ON A SURFACE THEREOF A COATINGCONSISTING OF A PROFUSION OR MICROSCOPIC, PRESSURE-RUPTURABLE CAPSULESHAVING WALLS OF GELLED FILM-FORMING HYDROPHILIC COLLOID MATERIAL INSUBSTANTIAL CONTIGUITY, EACH OF THE CAPSULES CONSISTING OF AN OILYWATER-IMMISCIBLE PRINTING FLUID AS A CENTRAL NUCLEUS AROUND WHICH HASBEEN EVENLY DEPOSITED BY COACERVATION FORCES A DENSE OIL-IMPERMEABLESHELL-LIKE COATING OF THE COLLOID MATERIAL, SAID CAPSULES BEINGRUPTURABLE BY PRINTING OR MAKING PRESSURES APPLIED TO THE CAOTED SHEET.